NAS (synology) found on Epson (Android) projector, but not on any iOS device

DSM version?

PMS version?

This indicates the server is not claimed by your account.

What is displayed in Settings → Server_Name → General?

It should say "Claimed by… " and your email address (or words close to that).

If unclaimed and DSM 7, see Synology FAQ - Questions, Answers, and How-To's - #39 by ChuckPa.